Welcome to the C3VR Vitaliy.
Congratulations on finding a 69 convertible! You will find lots of information on headers, exhaust and emissions in the C3 Fuel, Emission and Exhaust Systems Forum. There is where discussions of issues related to fuel, emission control, and fuel and exhaust systems are located. I have been reading the older post at this site for the past few months. Being new to working on cars I'm really learning this stuff from the ground up. Not having a garage, I do mean from the ground up.
I'm running stock exhaust on my 82 but, there are many members that are running a variety of headers, exhaust and emission-emissionless systems that should be able to advise. As to tone, I worked on guitar amplifiers for almost 3 decades and good tone (sound) to one may be awful tone to someone else.
Again, welcome to the forum and I am looking forward to seeing some pictures of your 69.
Keith
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Nobody ever waves when I'm driving the Explorer.
K Woody